OP ARTS AND SCIENCES. 95 



and phosphites, which hist are now generally considered as hydryl- 

 phosphinates, the general formula being 



11 .P0.(0H)2. 



On the other hand, the existence of alkyl-arsinic acids appears to 

 prove beyond a doubt that at least some arsenites belong to the same 

 type with the phosphites. The older view must in any case be true 

 for certain classes of salts, because the arsenites are not all reducible to 

 the type II . AsO . (Oil).,, even if we admit that the atom of hydrogen 

 is replaceable by an atom of univalent metal, for which there is no 

 sufficient evidence in the case of the phosphites. If we consider the 

 arsenic in the arsenoso-tungstates and arsenoso-molybdates which I 

 have described to exist in the form of hydryl-arsinic acid, we shall 

 have for the corresponding acids, respectively, the formulas 



18 WO, . A\R. AsO . (OFT) J . 8 11,0 

 16 WO3 . IG {[I . AsO . (OH)j . 9 II^O 



8 M06,, . 4 (H . AsO . (OHXJ . 3 lip 

 12 MoO^J . 10 {li . AsO . (OH)J . 3 II^O 



G M0O3 . 6 {II . AsO . (OII)^} . 3 lip 



in which, of course, the basicity is purely arbitrary, since it depends 

 in each case upon the number of molecules of base in a single salt. 

 The internal basicity, as measured by the hydroxy! in the arsenical 

 term, is always two, corresponding to one in the old style of writing. 

 As the salts described appear to give off all their water when heated 

 without other decomposition than loss from the volatilization of arse- 

 nous oxide, it would seem to follow that their formulas must then at 

 least be written as if they contained all the arsenic as AsoO., since 



2 {II . AsO . (Oil),} = As.O. + 3 up. 



PIIOSPHOROSO-PHOSPHO-TUNGSTATES. 



24 : 1 : 2 : 5 Potrtssic Phosphoroso-phospho-tungstate. — "When a solu- 

 tion containing both phosphorous and ortliophosphoric neids is added 

 to one of 12:5 sodic tungstate, no precipitate is formed, but on add- 

 ing potassic bromide a white crystalline salt is thrown down, slightly 

 soluble in cold water, but soluble in a large quantity of boiling water, 

 forming a turbid li(juid which has an acid reaction. The solution 

 gives no precipitate with cupric sulphate, even on boiling and with or 

 without free chlorhydric acid. It gives a white flocky precipitate with 



